We begin with a general overview of space oceanography, summarizing why it is so useful for ocean forecasting and briefly describing satellite oceanography techniques, before looking at the status of present and future missions. We will then turn to satellite altimetry, probably the most important and mature technique currently in use for ocean forecasting. We will also detail measurement principles and content, explain the basic data processing, including the methodology for merging data sets, and provide an overview of results recently obtained with TOPEX/POSEIDON and ERS-1/2 altimeter data. Lastly, we will focus on real-time aspects crucial for ocean forecasting. Perspectives will be given in the conclusion.